View source for 4rkn


==Wolinella succinogenes octaheme sulfite reductase MccA, form II==
<StructureSection load='4rkn' size='340' side='right'caption='[[4rkn]], [[Resolution|resolution]] 2.10&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4rkn]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Wolinella_succinogenes_DSM_1740 Wolinella succinogenes DSM 1740]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4RKN OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4RKN FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.1&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CU:COPPER+(II)+ION'>CU</scene>, <scene name='pdbligand=DTN:DITHIONITE'>DTN</scene>, <scene name='pdbligand=HEM:PROTOPORPHYRIN+IX+CONTAINING+FE'>HEM</scene>, <scene name='pdbligand=SO3:SULFITE+ION'>SO3</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=4rkn FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4rkn OCA], [https://pdbe.org/4rkn PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4rkn RCSB], [https://www.ebi.ac.uk/pdbsum/4rkn PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4rkn ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/MCCA_WOLSU MCCA_WOLSU] Respiratory sulfite reductase that catalyzes the reduction of sulfite to sulfide in a single step, consuming six electrons in the process (PubMed:22040142, PubMed:25642962). Required for sulfite respiration under anaerobic growth conditions (PubMed:22040142). Has only marginal activity with nitrite.<ref>PMID:22040142</ref> <ref>PMID:25642962</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The six-electron reduction of sulfite to sulfide is the pivot point of the biogeochemical cycle of the element sulfur. The octahaem cytochrome c MccA (also known as SirA) catalyses this reaction for dissimilatory sulfite utilization by various bacteria. It is distinct from known sulfite reductases because it has a substantially higher catalytic activity and a relatively low reactivity towards nitrite. The mechanistic reasons for the increased efficiency of MccA remain to be elucidated. Here we show that anoxically purified MccA exhibited a 2- to 5.5-fold higher specific sulfite reductase activity than the enzyme isolated under oxic conditions. We determined the three-dimensional structure of MccA to 2.2 A resolution by single-wavelength anomalous dispersion. We find a homotrimer with an unprecedented fold and haem arrangement, as well as a haem bound to a CX15CH motif. The heterobimetallic active-site haem 2 has a Cu(I) ion juxtaposed to a haem c at a Fe-Cu distance of 4.4 A. While the combination of metals is reminiscent of respiratory haem-copper oxidases, the oxidation-labile Cu(I) centre of MccA did not seem to undergo a redox transition during catalysis. Intact MccA tightly bound SO2 at haem 2, a dehydration product of the substrate sulfite that was partially turned over due to photoreduction by X-ray irradiation, yielding the reaction intermediate SO. Our data show the biometal copper in a new context and function and provide a chemical rationale for the comparatively high catalytic activity of MccA.

The octahaem MccA is a haem c-copper sulfite reductase.,Hermann B, Kern M, La Pietra L, Simon J, Einsle O Nature. 2015 Feb 2. doi: 10.1038/nature14109. PMID:25642962<ref>PMID:25642962</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4rkn" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Large Structures]]
[[Category: Wolinella succinogenes DSM 1740]]
[[Category: Einsle O]]
[[Category: Hermann B]]
[[Category: Kern M]]
[[Category: La Pietra L]]
[[Category: Simon J]]